1. Field of the Invention
The invention relates to three-dimensional data acquisition and more particularly to uses of superposition as a visualization techniques to aid in capture and refinement of three-dimensional data.
2. Description of the Related Art
A wide range of techniques exist for acquiring three-dimensional data from a subject. These techniques range from active techniques that actively control an imaging stimulus such as structured laser illumination, x-rays, ultrasound, or magnetic resonance) to passive techniques that operate directly on video data captured from one or more cameras. One broad category of techniques employs continuous scanning in which incremental three-dimensional data is acquired and assembled into a full three-dimensional model.
In this latter category, regardless of the particular sensing technology, a scanning process can be divided into abstract steps of incremental data capture, incremental derivation of three-dimensional data, and registration of the incremental data to a common coordinate system. The final registration step brings the incremental data together into a single three-dimensional model of a scan subject.
Current techniques generally separate acquisition from registration, with registration being performed in a post-processing step separate from data acquisition. While this permits relatively exhaustive processing, it poses a significant disadvantage because accuracy and completeness of the overall scan cannot be evaluated until after the scan has been completed. Unrecoverable errors or gaps in incremental data cannot be identified and fixed without initiating a new scan, possibly a full scan to completely replace the defective results. In commercial applications, where scheduling a common time and location for a scan subject and scanning hardware may pose logistical difficulties, this may increase the effective cost of scanning and inconvenience any parties involved.
In certain instances, this difficulty may be addressed by using robotics, independent references, or other techniques to determining the position of a scanning device within a global coordinate system. In addition to imposing further equipment costs, this approach can only be used to continue a previous scan if the subject of the scan has retained its position and orientation within the same global coordinate system.
There remains a need for real time visual feedback systems to support continuous three-dimensional scanning. There also remains a need for improved guidance and visual feedback systems for use with particular three-dimensional imaging applications, such as digital dentistry.